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Question DetailsAsked on 1/14/2017

Lighting fixture

I just installed a lighting fixture that says to use a PAR 20 light bulb, however I want to use a lifx A19 LED light bulb. Is it ok to use a A19 light bulb in a fixture that recommends using a PAR 20?

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Generally NO, and absolutely not if an incandescent bulb ! note - in light fixtures, a bulb designation is not a "recommnedation" - it is requireds to meet the conditions under which the fixture is approved by the UL or other rating organization,. use the wrong type bulb or too much wattage and you can very easily have a serious safety issue, especially since the rating agencies like UL allow such small wire and shoddy insulation in lamps, and allow the wiring into the light bulb socket to be exposed to the heat of the bulb, which can get extreme in inverted (open end down) lighting cans and track lights.


The PAR designation indicates it has a parabolic reflector - common type bulb for a recessed ceiling fixture or can light, which has a parabolic shaped mirror surface up inside at the base of the glass and in the lower portion of the glass, to reflect most of the light going radially out or up toward the base back down to the larger, rounded end of the bulb to provide a spot or flood light effect and direct most of the light effectively out of the light fixture, rather than wasting it inside the can and heating it up.


There are also regular reflector types (type R) that are basically almost flat-faced or only slightly rounded faced which are designed to fit about flush with the can openign or face, and BR type which means Bulged Reflector, meaning the ovalized or rounded "light" end sits forwards of the can a bit and by sticking out of the can a bit provides more of an overall wide-angle or flood effect. There are also spot type reflector bulbs, with varying number of degrees of angle coverage of the primary lighting - normally used for highlight illumination of artwork or for entertainment events like stages and movie sets and such.


The 20 number is the diameter of the bulb, in 1/8'ths of an inch - so yours is a 2.5" bulb (for a mini can or track light), probably designed to fit a 3 or 3.5" can. (Needs to be clearance around it for some ventilation or it will fry very quickly - so you need to follow the manufacturer recommendation on the maximum bulb size allowed, AND the maximum wattage - otherwise you can cause a fire or fry the insulation on the wiring up in the can.


One other thing - never use a high intensity discharge or halogen bulb in a fixture not rated for it - they used to come with radically different pin connections only, but now are coming out in conventional screw base too, so there have been an increasing number of fires caused by HID or halogen bulbs in fixtures not rated for their heat, which is almost always far above that of incandescent bulbs even.


Now the crux of it - those you have now are R class or reflector type bulbs (reflector in the base) to direct almost all the light down out of the can, rather than all around. An A19 or any type A Edison type bulb shape (the A means Arbitrary Spherical Shape, meaning basically roundish bulb), your normal traditional household light bulb shape, is designed to give all-around lighting except past the base - generally about a 150 degree lighting arc drawn from along the central axis at bulb "light" end down each side towards the base. In a can that will waste much of the light, plus likely dramatically overheat and possibly short out - and most A type bulbs are not even rated for inverted use (upside down, with glass down) anyway. You would most likely, in addition to wasting light, burn up the electronics in the ceramic base, which creates a REALLY nasty smell that can persist for weeks, as well as being a potential fire risk.


What you need if you want LED lighting in that fixture is still a PAR20 or possibly BR20 rated bulb but in LED type, rated for track light or recessed can use (because the heat gets trapped up in the can so has to be able to handle the heat), AND there are five other selection factors:


1) right total length so when screwed into the can or track housing the face of the bulb is roughly flush with the face of the can rather than nsticking way out or way up inside, or for BR type the bottom of the rounded end (where the sides begin to slope down to the base) should be at the face of the can or slightly protruding so the light can spread out without being blocked by the can. However, if subject to possible contact by any item or a person's head, bulb should not protrude from the can so don't use a BR type.


2) neck shape - if your can is a stepped type - smaller diameter near the top than at the open end, you need not only the right length bulb but also a long-neck bulb, because the bulb housing on a regular neck one may not fit up in your can without hitting the shoulder of the smaller-diameter part of the can - stepped cans need a long straight extension on the base of the housing above the base before it starts to flare out to the "bulb" part.


3) wattage - because LED and CFL bulbs use a lot less electricity than comparable incandescent bulbs, they are rated for input wattage andalso for the equivalent incandescent bulb they replace - which is very loosely (much looser with some manufacturers than others) based on the lumens or amount of light it puts out. One would think you could just go with a CFL or LED bulb which does not exceed the rated capacity of the incandescent bulb - but that is not the case, because some of them overheat in inverted and especially in closed can situations - so you need to check manufacturer info on that. In some cases that recommend use only in vented cans (with air vents in the top), in others a minimum clearance around the bulb and/or maximum depth of can when in inverted (upside-down) use. I have found by experience that if I stay two bulb wattage rating below the incandescent number with CFL's and one with LED's they generally do not cause problems - so say the ficture is rated for max 75W incandescent, I use not more than a 50W input CFL or 60W LED bulb - which would actually be WAYYY brighter than a 75W incandescent anyway, because normally for equivalent light of a 75W bulb a CFL or LED would be about 13W in LED or about 18-20W draw in CFL bulbs.


4) if the can is inverted and enclosed (no air vents in the top), make sure the bulb is rated for enclosed can use. Otherwise if it needs the venting to release the waste heat (and CFL and some LED bases get fairly hot) it will probably fail pretty quickly and may be a fire hazard.


5) bear in mind that like normal flourescents, CFL and LED lights do not being turned on and off - starting one can be equivalent to many hours of usage in wear and tear, so don't use in applications like bathroom lights or entry lights which are turned on for only a minute or two then turned back off as frequent intervals. They are ideal for porch lighting, always-on area night lighting, grow lights (using the correct spectrum), and the like where they are turned on and off infrequently. I found CFL and LED bulbs lasted no longer than incandescents, if that long, in "passing by" locations like halls and bathrooms where they are turned on and off several times a day but only for a minute or few, typically a year or so in porch light use (on and off one daily on a sensor), and 3-4 years of continuous on service as a nightlight (24 hour) in darkish locations or stairwells. That life factor of course also affects whether they are actually cost effective or not, considering they typically cost 2-10 times as much as normal incandescent bulbs.


BTW - CFL bulbs come in reflector type too, but not as effective in directing the light downward as an incandescent bulb because the spiral CFL tube gets in the way, so you generlaly need a higher equivalent rated bulb to get the same amount of light on the target - commonly by 1-2 equivalent incandescent bulb wattage ratings.


I recommend going to the G7 Power website (G7power.com) for examples and explanation of long-neck versus standard neck bulbs, and the various angles of illumination from different types of bulbs, depending on whether you want them for flood lighting, general lighting, illuminating a feature on the wall, a defined fine pinpoint spot for a painting or for grow lights, or whatever. Easy to tell which bulbs are theirs because all are named after a town in Nevada (where they are based). I have used their bulbs in track cans and recessed cans for about 2 years now - like all LED light bulbs for household use they only last about 15-20% the promised number of hours before some of the LED's go out (commonly have about 7-9 individual LED "lights" per bulb) and overall are effective for maybe 25% of their promised life before they loose enough LED's to not provide the desired illumination - but that is way better than many of their competitors, and they do quickly replace ones that do not meet the promised life. I get mine from Amazon - about half the cost of stores. I have made a study of different LED/CFL brands since they started coming out, and CREE and G7 (I thing they use CREE LED's) seem best, GE next but quite a bit behind, and the rest I have tested (Phillips and Sylvania and off-brands) seem to be pretty much junk - generally not even lasting as long as a cheapo regular incandescent bulb - maybe 200-800 hours at best, versus the typically 10,000-25,000 hours promised, and commonly dramatically overheating or even exploding.

Answered 1 year ago by LCD




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